International projectionist (Nov-Dec 1933)

14 INTERNATIONAL PROJECTIONIST November 1933 graphite anode and subsequent getter action. 3. Higher plate dissipation without overheating. 4. Lower operating temperature at anode, resulting in lower operating temperature of other electrodes, preventing primary and secondary emission from grid. 5. Comparative freedom from gas, eliminating positive ion bombardment of filament especially destructive in the case of thoriated tungsten filament. 6. Uniform characteristics at all times and throughout long life, due to rugged anode and its non-warping feature. 7. Longer life and therefore greater economy in operation. It is believed that this graphite anode development marks the most outstanding tube development since the introduction of the thoriated tungsten filament several years ago. The advantages of graphite are such that graphite elements may be increased in number and perhaps extended even to the smaller tubes in time. Meanwhile, however, the introduction of the graphite anode in such popular sound system tubes as the 205D, the 242A, the 258A rectifier and others, brings a new standard of performance and life into this important field of tube applications. FEATURE TITLE EMBELLISHMENT Hugo Lateltin MEMBER, I. A. LOCAL 306, NEW YORK CITY lyf ANY theatres use special effect machines for the embellishment of feature titles. Commonly, a slide is projected on the screen through a gelatin filter or through a color wheel. The variety of changes and patterns obtainable with slides is necessarily limited. The mechanism described in this article provides a means for introducing a number of novel variations in lighting effects. The construction of the apparatus is simple and may be done at low cost. It can easily be made by a projectionist possessing some mechanical skill and who is interested in creating new stage effects and feature title embellishments. The mechanism consists of an attachment applicable to any standard effect machine. It can be slid into the front holder (Fig. 1, H), of the lamp house. This holder usually measures 8x9 inches. A base plate (Fig. 1, B), is held rigidly by the back plate of the attachment. This back plate has to fit into the holder and should be provided with set screws at each corner to prevent the mechanism from wabbling. The base plate carries all the removable parts of the mechanism, such as color wheel, slide holder and any mirror attachments which may be used for different effects. Runners at the sides of the base plate make possible the free shifting of the removable parts. Component Parts Figure 1 shows a cross-sectional view of the mechanism. H is the front holder of the lamp house. C is a color wheel driven by a motor, T. If A.C. is available, a Telechron Clock motor has been found most reliable for the driving of the color wheel. S represents the slide holder, while K is a kaleidoscope, consisting of three mirrors. L is the projection lens which on all effect machines is firmly connected with the base structure of the machine. The focal distance lies mostly between 15 and 20 inches and therefore provides ample space for the introduction of different mirror arrangements between the slide carrier and the lens. It is best to cut the length of the mirrors just short of the focal length. This utilizes all the light coming through the slide. For ordinary purposes, plain mirrors of a fairly good grade of glass are quite suitable. If a sharp effect is desired, surface mirrors have to be used. Such mirrors can be obtained from any silvering establishment by specifying surface mirrors. These mirrors are silvered in the usual way, but the silvered surface should not be touched with shellac or paint, as this side will be used for reflection. Careful handling is necessary. The unprotected silver oxidizes slowly and can be used for reflection only for a few months. Figure 2 shows a perspective view of the mechanism. At the right you see the back plate which fits into a lamp house holder. An opening in this plate